2.1.3 Amount of Substance

Question 1

empirical formula

Answer 1

the simplest whole number ratio of atoms of each element in a compound

Question 2

molecular formula

Answer 2

the actual number of atoms of each element in a compound

Question 3

how to calculate empirical formula

Answer 3

-make table with mass, Ar, moles, ratio
-put elements on top
-based off ratio you can put empirical formula

Question 4

how to calculate empirical formula when given percentages?

Answer 4

consider mass percentage

Question 5

how to calculate molecular formula from empirical formula and mr?

Answer 5

-calc mass of E.F
-divide mr by that mass
-times each E.F by that number

Question 6

ideal gas equation?

Answer 6

pV = nRT

p = pressure Pa
V = m^3
n = moles
R = universal gas constant 8.31 Jk^-1mol^-1

Question 8

how to do a titration?

Answer 8

1. add known 25cm^3 of alkali solution liquid to a conical flask using a pipette
2. set up a burette above conical flask, fill with acid of a known concentration
3. add indicator to conical flask
4. note starting burette volume
5. add solution from burette & swirl flask
6. stop titration when indicator changes colour
7. record final burette volume
8. calc how much added
9. repeat w more care, go slowely for last 2-3cm^3